Last year I picked up My Wilderness: East to Katahdin by Supreme Court Justice William O. Douglas (1898-1980). It's one of those books you can just dip into occasionally and enjoy in odd moments because each chapter is devoted to one of eleven wilderness areas in the U.S.
You may know that Douglas was an outdoorsman who loved to hike and fish and canoe, and he had friends who were wilderness guides. He knew plants and animals like a naturalist so when he takes the reader on a trip through an area like the White Mountains, for instance, he points out flowers, wildlife, geological features, dangers and outstandingly beautiful sites. His descriptive passages are written like a poet, yet sometimes he'll weave into it something appropriate from the law.
The book was published in 1961, at which time most people weren't thinking about saving the environment. Like a prophet, he was literally a voice in the wilderness warning about the threat to wilderness areas from roads, clear-cutting, and overuse. On page 56, Douglas quotes Lorus J. Milnes' The Balance of Nature(1961), "By obliterating other kinds of life, man may be destroying himself as well."
Above all else, Douglas loved to fish, especially for rainbow trout. Not the stocked trout available in most places today, but native fish. Everywhere he goes he fishes the streams and lakes, noting the water birds, surroundings, and joys of landing a big one. Some of the best passages are about the guides he has known and their well-honed skills in a boat or on a trail. He praises National Forest Service employees while condemning National Forest Service policies which at the time were allowing many roads to be built and, worst of all, clear-cutting of national forest.
I know this is an old book, but if you love nature or memoirs of people who are passionate about their topic, keep an eye out for it at book sales and used book shops.